How it works
HMRC has rules. We apply them. You get a number.
UK crypto tax is not just a matter of “what did you make minus what you paid.” HMRC specifies exactly how sales must be matched against purchases — and the order matters. Get it wrong and you either overpay or underpay.
Here is exactly how we calculate your tax, in plain English.
Import your transactions
We need to know every time you bought, sold, traded, received, or sent cryptocurrency. The more complete your data, the more accurate your calculation.
You can import via three methods: connect your exchange with a read-only API key (syncs automatically), upload a CSV export from any exchange (we auto-detect the format), or paste an Ethereum or Bitcoin wallet address for on-chain transactions.
Binance, Coinbase, Kraken, Bybit. Set up once, syncs automatically.
Any exchange export. We detect columns and date formats automatically.
ETH and BTC on-chain. Historical GBP prices fetched automatically.
Add any transaction by hand. Useful for older trades or unusual events.
What counts as a transaction
We apply HMRC's matching rules — in the correct order
When you sell crypto, HMRC does not let you choose which purchase you are selling against. It specifies three rules that must be applied in sequence. Every rule must be checked before moving to the next.
Same-day rule
Why it exists: This rule prevents a simple tax avoidance strategy: sell crypto at a high price, immediately buy it back at the same price, and claim the full gain as having zero cost.
How it works: If you buy and sell the same cryptocurrency on the same day, those transactions are matched against each other first — before any other matching takes place.
Worked example
You own 2 BTC from previous purchases (average cost £25,000 each). On Tuesday you sell 1 BTC for £45,000 and later the same day buy 1 BTC for £44,000.
Result
The Tuesday sale is matched against the Tuesday purchase. Your gain is £45,000 − £44,000 = £1,000. The 2 BTC you already owned are untouched.
30-day rule
Why it exists: Named after an old shares tax avoidance practice where investors would sell at year-end to crystallise a gain or loss, then repurchase the next day. HMRC extended the look-ahead window to 30 days to prevent the same thing with crypto.
How it works: If you sell a cryptocurrency and then repurchase the same asset within the following 30 calendar days, the sale is matched against those later purchases (in date order, earliest first). Only applies to purchases after the sale — not before.
Worked example
You sell 1 ETH on 1 March for £2,800. You buy 1 ETH on 20 March for £2,600. You also owned ETH from a purchase in January at £1,500.
Result
The 30-day rule applies. The 1 March sale is matched against the 20 March purchase. Your gain is £2,800 − £2,600 = £200. The January ETH is not used.
Section 104 pool
Why it exists: The Section 104 pool is the main rule for most crypto disposals. It treats all your purchases of a single asset as one pool with an average cost — you cannot cherry-pick the most expensive coins to sell.
How it works: We maintain a running total of your quantity and total cost for each asset. When you add (buy, receive), both increase. When you dispose (sell, trade, gift), you use the average cost per unit across the whole pool.
Worked example
You bought 1 BTC at £20,000 in 2022 and 1 BTC at £40,000 in 2024. Your pool: 2 BTC at a total cost of £60,000. Average cost: £30,000 per BTC.
Result
You sell 1 BTC for £45,000. Your cost basis from the pool is £30,000. Gain = £45,000 − £30,000 = £15,000. Pool now: 1 BTC at cost £30,000.
You see your number — free
Once your transactions are imported, we run the calculation across every tax year in your history. You see your total gains, total losses, net gain, and — most importantly — how much is taxable after your annual allowance.
If you are below the £3,000 annual exempt amount, you likely do not owe anything and may not need to report at all. You find that out before you spend a penny.
If you owe tax, or you want the full report to file your Self Assessment, the Standard plan is £49 a year and covers all tax years. It follows the HMRC SA108 layout so the figures go straight onto your return.
What you see for free
What the Standard plan PDF adds
Common questions
Do I need to report crypto to HMRC even if I made no profit?
Not necessarily. If your net gains are below the £3,000 annual exempt amount and your total disposal proceeds are below £50,000, you generally do not need to report. However, you should always keep records in case HMRC asks.
What if I lost money on crypto?
Losses are valuable. They reduce your gains for the year — and if your losses exceed your gains, you can carry the remaining losses forward to offset against future gains. You need to report the loss to HMRC to preserve it, even if you owe no tax.
I traded crypto-to-crypto. Is that taxable?
Yes. HMRC treats a swap of one cryptocurrency for another as a disposal of the first asset and an acquisition of the second. The disposal may generate a gain or loss, just as if you had sold for GBP.
What about coins I lost access to or that became worthless?
You may be able to claim a negligible value claim for assets that have become worthless, effectively crystallising a loss without a sale. If you lost access to coins (lost private key, exchange failure), speak to a qualified tax adviser as the treatment depends on the specific circumstances.
I have transactions going back years. Do I need all of them?
The Section 104 pool accumulates from your very first purchase. For an accurate calculation, you should import all your historical transactions. If you are missing some, you can add them manually. Incomplete data leads to inaccurate results.
What is the deadline for paying crypto tax?
If you file Self Assessment, the deadline for reporting and paying is 31 January following the end of the tax year. So for the 2024/25 tax year (which ended 5 April 2025), the filing deadline is 31 January 2026.
Ready to see your number?
Import your transactions and we apply all three rules automatically. Free to see your gain.